The present invention relates to diamond styli for video disc players and in particular to an improved method for manufacturing such styli.
In U.S. Pat. No. 4,165,560 which issued on Aug. 28, 1979 to Yasushi Matsumoto for METHOD FOR MANUFACTURING A DIAMOND STYLUS FOR VIDEO DISC PLAYERS a method is disclosed for the manufacture of video disc styli. Such styli are used in the playback of video discs in a system such as that disclosed in U.S. Pat. No. 3,842,194 which issued on Oct. 15, 1974 to J. K. Clemens.
In the method disclosed in the Matsumoto patent, a conical shape is ground at one end of a square diamond shaft and a flat electrode-bearing surface is then ground into the conical surface. A record engaging surface is then ground cross-wise at a right angle to the electrode-bearing surface following which two converging flat surfaces are ground. Finally a metallic coating is deposited on the electrode surfaces of the diamond. In the resultant stylus, the record engaging surface is disposed substantially orthogonally to the electrode-bearing surface. Thus, the grinding steps described above are performed to provide a record engaging surface having the needed relationship to the electrode surface.
As will be readily apparent to those familiar with the diamond grinding art, the cost of producing a particular configuration is related to the mass of diamond which must be precisely removed. Thus, while diamonds may be rough cut to remove large quantities of diamond at relatively moderate expense, where precise surface relationships are required, precise grinding techniques must be employed which greatly add to the cost of the final product.
The conical grinding operation discussed in the Matsumoto process is one which is relatively simple and may be performed as a rough grinding operation on commercial grinding machines. The grinding of the remaining faces, however, requires precise grinding techniques which add substantially to the cost of the final stylus.
In view of the above, it is a principal object of the present invention to provide an improved method for producing a diamond playback stylus of the type discussed above in which a major portion of the material to be removed may be rough ground leaving only relatively small portions requiring precise grinding;
A further object is to employ such a method to produce a playback diamond stylus which has comparable performance characteristics to styli produced by other grinding techniques, while affording a substantial cost saving over such other techniques;
A still further object is to provide a method which utilizes conventional grinding equipment and procedures.